Evolution doesn't have to operate at a snail's pace, even for snails. In experiments designed to simulate the evolutionary transition that produced slugs, researchers exposed baby snails to the metal platinum, causing the animals to develop without external shells. The research illustrates how a big leap on the evolutionary path of animal body plans might have occurred. It also reopens a can of worms concerning the development and evolution of an entire class of shelled creatures.

Scientists reared Marisa snails, best known for cleaning up algae and other debris in home aquariums, in petri dishes containing varying concentrations of platinum. At certain exposures, all of the roughly 80 percent of snails that survived were shell-less, Heinz Köhler of the University of Tübingen in Germany and his colleagues report in the September-October Evolution & Development. The researchers posit that the platinum is causing effects similar to the genetic mutation that turned off shell production in some snails, paving the way for their slug descendants.

"This shows that you can get really dramatic changes that could be similar to the genetic mutations that drive evolution, without worrying about doing everything in small incremental steps," says comparative physiologist Roger Croll of Dalhousie University in Halifax, Nova Scotia. "This is a very concrete demonstration, a very clear demonstration of a large-scale change in body plan. All of a sudden you get shell-less animals."

Evidence suggests that transitions from snails to slugs — or rather, from having a concrete outer shell to a greatly reduced internal one — have happened numerous times in evolution. Such losses or gains occurred repeatedly within the Mollusca, an enormous group that includes clams, oysters, squid, octopuses and of course the gastropods —snails and slugs. The internal flat bone of cuttlefish and squid, for example, is thought to be a pared-down version of an ancestral outer molluscan shell. And the shell game continued within the gastropods. Within the marine gastropods known as sea butterflies and sea hares, for example, there are both shelled and shell-less species.

Though the new study shows that shell loss in gastropods can happen in one fell swoop, it also suggests that another evolutionary transition might have required several steps to complete. Torsion is an anatomical hallmark of the gastropods that makes them look like their bottom halves were rotated 180 degrees relative to their top halves, putting their anuses over their heads. The term torsion also refers to the hypothetical evolutionary process that purportedly led to this awkward anatomy, says evolutionary biologist Louise Page of the University of Victoria in British Columbia.

The new research suggests that torsion might not have occurred in one grand swivel. In many gastropods the anus, gills and mantle cavity are rotated 180 degrees. But in some there is partial rotation. And in the snails that Köhler and his colleagues exposed to platinum there was partial rotation as well: The anus swiveled but the gills and mantle were left in their original positions. This suggests that the gastropod body plan could have arisen through physiological means other than torsion, such as asymmetrical growth, where one half of the body atrophied and the other blossomed.

"This paper helps people to think about the fact that these anatomical positions are not necessarily coupled together," says Page. "It really demonstrates that development is modular, that you can have quite drastic modifications of the development of one component of the body plan but not others."

Piles of bones and historical records tell us the Black Death pandemic wiped out as much as half the population of Europe during the Middle Ages. But how and what, exactly, caused the grisly scourge has sparked a boxing match of sorts within the pages of scientific journals.

The final bell has rung, according to a new study, and the bubonic plague — which is caused by a bacterium also known as Yersinia pestis — is the winner. What's more, the authors say the same bacteria caused smaller outbreaks during the next four centuries throughout Europe.

"Our data … ends the debate about the etiology of the Black Death, and unambiguously demonstrates that Y. pestis was the causative agent of the epidemic plague that devastated Europe during the Middle Ages," the authors wrote in the Oct. 7 issue of PLoS Pathogens.

The bubonic plague makes its first deadly appearance in historical records during the sixth century, and scientists and historians have long eyed it as the culprit of the Black Death that went down from 1347 to 1353, as well as of other plagues throughout history. But uncertainty in genetic data has produced other suspects, including viral hemorrhagic fever or some yet-to-be-discovered disease.

If left untreated, a bubonic plague infection can kill a person in as little as two days, either by causing lymph nodes to burst and flood the bloodstream, or by attacking lung tissue to cause pneumonia. Most often, the disease is spreads by fleas that are carried around by rodents. In either case, the bacteria's genetic signatures can be found in bones long after a victim dies.

To build their case, the study's authors extracted DNA from more than 75 skeletons in mass graves or plague pits across Europe. As an added measure, the scientists compared the samples to bones in nearby regions unaffected by the disease. All of this data, according to the study, points to bubonic plague as the cause of the 400-year-long pandemic and not other diseases.

The impulse to be social is so deep-seated in human consciousness that it's even evident in the womb, suggests a new study on the interaction of twins just a few months after conception.

Twin pregnancies offer "the unique opportunity to explore social behavior before birth," wrote researchers led by psychologist Umberto Castiello of Italy's University of Padova. "Newborns come into the world wired to socially interact. Is a propensity to socially oriented action already present before birth?"

The researchers used ultrasound recorders to make three-dimensional videos of five pairs of twins, once at 14 weeks and again at 18 weeks. By the 14th week, they were already reaching for each other. This was even more pronounced by the 18th week, when fetuses touched each other more often than themselves.

Though some contact is inevitable between two growing bodies sharing a confined space, kinematic analysis showed that fetuses used distinct gestures when touching each other, rather than touching themselves or uterine walls. Their hands lingered.

"Performance of movements towards the twin is not accidental," wrote the researchers. Their findings were published Oct. 7 in Public Library of Science One.

Earlier research had shown that within hours of birth, newborns already imitate the facial gestures of other people, indicating an inborn capacity for social behavior. The researchers call this "the social pre-wiring hypothesis."

The findings "epitomize the congenital propensity for sociality of primates in general and of humans in particular," wrote the researchers. Put another way, it's human nature to reach out and touch someone.

Image: Video frames representing a fetus reaching towards and "caressing" the back (left) or head (right) of a sibling./PLoS One.

On the Martian surface, the mountains are high and the canyons are low. Really, really low.

Not only is the martian volcano Olympus Mons the highest peak in the solar system, Melas Chasma, the canyon pictured above, is the deepest in the solar system. In this image from the European Space Agency's Mars Express orbiter, the valley on the left (darker area) sits a whopping 5.6 miles below the plateau on the right (lighter area).

Compared to the average shape of Mars, known as the "aeroid," the canyon floor sinks down about 3.1 miles. Planetary scientists would love to use sea level measurements to describe Martian surface features, but there's no ocean on the red planet anymore and any signs of an ocean are long since warped by millions of years of surface deformation.

The photo above covers about 7,700 square miles, or about the size of New Jersey, which makes it only a tiny postage stamp of Mars' deepest, longest and most prominent scar — the 2,500-mile-long Valles Marineris rift valley (below).

ESA also released the following 3-D rendering of Melas Chasma in addition to the satellite imagery, revealing the valley in all its topographical glory (via Nancy Atkinson at Universe Today).

Autism seems to play a genetically inspired hide-and-seek game in some families. Undiagnosed siblings in families that include two or more children with autism often grapple with language delays, social difficulties and other mild symptoms of the disorder, a new study suggests.

Genes prompt autism symptoms of varying intensity among members of these families, including in some kids who don't qualify as having an autism spectrum disorder, say psychiatrist John Constantino of Washington University School of Medicine in St. Louis and his colleagues. Researchers have generally limited their search for DNA peculiarities to children diagnosed with autism or related disorders, a strategy that overlooks those with mild autism signs, Constantino's group asserts in a paper published online October 1 in the American Journal of Psychiatry.

"Subtle aspects of the autistic syndrome have not been accounted for in most studies of its intergenerational transmission," Constantino says.

By including individuals with mild autism symptoms in DNA studies, researchers could enlarge their sample sizes and amplify the statistical power of studies to find genetic effects, remarks psychiatrist Joseph Piven of the University of North Carolina at Chapel Hill.

"Given Constantino's data, it is clearly wrong to label all nonautistic individuals as unaffected by an underlying genetic liability for the condition," Piven says.

Approximately one in five siblings of children with autism who don't meet criteria for the disorder display mild or "subclinical" autism traits, Constantino's team estimates. These traits consist of language delays, the use of odd or repeated phrases and other unusual speech qualities and difficulties interacting with others. Most such children come from families with at least two other youngsters who have an autism spectrum disorder.

Four times as many boys as girls meet psychiatric criteria for autism. But the inclusion of mild autism traits narrows that ratio to three boys for every two girls.

Males and females inherit the same autism-related genes, but in females those genes frequently interact with other genetic factors or with environmental influences to reduce the severity of symptoms, Constantino theorizes.

Subclinical autistic traits deserve close scrutiny for possible detrimental effects on children, Constantino adds. Kids with undiagnosed autism-related social deficits may find it hard to make friends and could experience a worsening of other conditions such as learning disabilities and attention-deficit hyperactivity disorder.

Subclinical traits may have benefits as well, he adds. Disinterest in social activities and a focus on details might boost math, science and computer skills.

Constantino's team assessed signs of autism in 2,920 children from 1,235 families participating in a national online research registry. Each family in the registry includes at least one child with an autism spectrum disorder and at least one biological sibling. Data came from questionnaires completed by parents.

Their responses indicated that 134 families, or 11 percent, had more than one child diagnosed with autism. About one in four families, including nearly all of those with multiple autism cases, also contained siblings with mild symptoms.

Among mildly affected boys and girls, 20 percent had received a diagnosis of language delay or speech problems early in life, double the prevalence in the general population.

Constantino emphasizes that, for three in four families, one child had an autism spectrum disorder and the rest showed no signs of autism. He suspects that autism-related genes work in an all-or-nothing fashion in these families.

Clinicians should measure the intensity of autism symptoms over time in individual children and determine points at which interventions become necessary, much as they use growth charts to ascertain childhood obesity, he recommends.

This area of Mexico recently underwent a change in agricultural practices that has had an impact on the region so great that it can be seen from space.

These images, taken by the Landsat satellite in 1992 (left) and 2010 (right) show how increased use of water from a major reservoir has affected this part of the state of Chihuahua. Most drastically, a switch to center pivot irrigation shows up as bright red circles. The water is being used for growing alfalfa and sorghum to feed livestock.

Diverting more water from the reservoir has also affected native vegetation in the area and reduced the amount of water flowing into the Rio Grande River.

Seals diving for their dinner near Antarctica have surfaced with an extra morsel: information, gathered by electronic tags on the animals' heads, about the shape of the seafloor there.

The work has revealed previously unknown undersea channels, through which warm water might flow toward fragile ice shelves. And the seals do it all for a fraction of the cost of traditional seafloor mapping done from ships.

"It gives you a much denser picture of what the water depth is than anything you can conceivably do with ship tracks," says Laurence Padman, an oceanographer at Earth & Space Research in Corvallis, Ore., and a coauthor of an upcoming paper in Geophysical Research Letters describing the technique.

Seals, walruses, whales and other large marine creatures have moonlighted as oceanographers before. Scientists typically glue sensors to the animals' bodies that measures factors like temperature and salinity. Researchers have used this information to study water temperatures around Greenland, among other topics.

But the new work is the first to extract information on the shape of the seafloor — known as bathymetry — from the sensors, which also measure pressure and hence depth. "You can actually map the ocean floor," says team member Daniel Costa, a marine biologist at the University of California, Santa Cruz.

The data came from 57 elephant seals, tagged by Costa's group over five summers at the U.S. Antarctic Marine Living Resources camp in the South Shetland Islands. As the animals swim, the tags record information every few seconds, then relay it via satellite once the seals surface. About 30 percent of the time seals dive all the way to the bottom to forage for food, says Padman, so by studying enough dives for each animal — some 200,000 dives in total — the researchers can deduce where the seafloor lies.

"It's a novel and useful technique for gathering bathymetry data," comments Paul Holland, an ocean modeler at the British Antarctic Survey in Cambridge, England.

Within the seal data Padman's team discovered several significant troughs cutting across the continental slope off the west side of the Antarctic Peninsula. These features hadn't been mapped before, says Padman, yet they play an important role in ocean circulation. Warm water can flow through such channels and up under the floating ice shelves that extend off Antarctica, such as the Wilkins ice shelf that partially disintegrated in 2008.

Better information on underwater topography could lead to improved models of how the ocean will respond to climate change, says Padman.

Other researchers might now be inspired to dig through seal data to see what features could be mapped, he adds. Ships can cost tens of thousands of dollars a day to operate in Antarctic waters, whereas there is a wealth of readily available information available on seal tags.

"We want to encourage other people who work with seal data to look into it," says Padman. "We just thought it was really cool."

Some of these have already appeared on Wired Science (and spent weeks as this reporter's desktop background), but many are new to us. ESO comprises a constellation of telescopes high in the mountains of Chile, including the Very Large Telescope (actually four separate telescopes working together), VISTA, APEX, the La Silla Paranal Observatory, and ALMA, so there were a lot of images to choose from. Some of the most striking are of the telescopes themselves — the scenery in the Chilean desert is as stunning as its skies are clear.

And some lucky astronomy buff will get to go there. ESO just announced a contest they're calling "Hidden Treasures" for the best images dug out of their archives. Once you've chosen an image (or several!) you can process or enhance it any way you want, aside from painting directly on the image.

"The goal is to dig a dataset out of the ESO science archive, process the raw frames and assemble them into a stunning color or greyscale image," the website explains. "Can you compete with the best astrophotography specialists?"

The grand prize: an all expenses paid trip to the VLT on Cerro Paranal in Chile, where the winner will get to participate in VLT observations. I'm already jealous.

A model earthquake on a lab bench shows that a basic assumption of introductory physics doesn't hold up at small scales. The finding could have a wide variety of implications for materials science and engineering, and could help researchers understand how earthquakes occur and how bad they might be.

"Our group has recently devised a way to look at laboratory generated earthquakes as they take place," said physicist Jay Fineberg of the Hebrew University of Jerusalem. "On the way, we found out that many of the assumptions people have used historically in investigating this stuff… are basically wrong. They don't work."

For centuries, physicists have thought that the amount of force needed to start a book sliding across a table is equal to the force from friction that keeps book and table stuck together. That frictional force is determined by a number called the coefficient of friction, which is the ratio between the forces pushing sideways and pushing down (basically, how much the book weighs).

But when Fineberg's student Oded Ben-David, first author of a paper in the October 8 Science describing their experiments, tried to reproduce them in carefully controlled lab experiments, the laws fell apart. Ben-David found that he could apply up to five times as much sideways force as the coefficient of friction predicted, and the book still wouldn't move.

"Even in the lab, he couldn't predict what was going to happen," Fineberg said. "Small, crazy details made a really big difference. "

The team's experimental setup was "the stupidest system you could think about," Fineberg said. The physicists pressed two 8-inch-long blocks of Plexiglass together with tons of force, and pushed the top block sideways until it started to move. Sensitive sensors called strain gauges measured the amount of stress on the blocks in every direction. A combination of lasers and high-speed cameras tracked the points where the two blocks actually touched.

"We're the first people who ever tried this," Fineberg said. "Technically it's a bit difficult to use, but we figured it out and it's no biggie, it's doable."

Although the blocks looked like they were smoothly connected along the whole area between them, in reality there were only a few hundred tiny contact areas. The forces on each individual contact could get much bigger than the coefficient of friction allows before the contacts ruptured and the block began to slide.

"These blocks are optically flat, we spent thousands of dollars to make them that way. Even then, small nuances entirely change the dynamics of what we're going to see," Fineberg said. "If this is in a lab experiment, imagine what happens along an earthquake fault, which is a really crappy experimental system."

Breaking the contact sent waves similar to sound waves rippling through the blocks, which resemble a miniature earthquake, Fineberg says. The blocks represent two tectonic plates sliding slowly against each other, and when the sliding force is enough to pull the plates apart, it sends shock waves through the earth.

"It's exactly the same system, just scaled up by factors of thousands," Fineberg said. "We can watch how these things unfold and measure all the variables that might be actually relevant, that there's no way you can get to under the earth."

The team found that the waves come in three distinct modes: slow ruptures that move at speeds well below the speed of sound in the glass; "sub-Rayleigh" ruptures that travel at sound speeds along the surface, which Fineberg describes as "your garden variety earthquake;" and "supershear" ruptures that go much faster than expected. Which type of wave you get is determined by the stresses at the contact point, which provides a measure of how much energy would be released if an earthquake were to begin there.

An earthquake moving at supershear speeds would cause a sonic boom. Some think the earthquake that hit Izmit, Turkey in 1999 was this kind of deadly quake, but not everyone is convinced that supershear earthquakes actually exist.

"I think one of the most exciting things about this paper is the fact that they see a whole range of behaviors in one system," commented geophysicist Chris Marone of Penn State University, who was not involved in the new work. "People had seen different parts of this in different experiments in different configurations. But this is one of the first, if not the first time that people have seen all the different ranges of behaviors in one place."

It's still impossible to make detailed measurements of the stresses along a real fault, Fineberg points out. But current technology can track stresses as an earthquake is under way, and one earthquake can affect the initial conditions for the next one. Once there are measurements for one earthquake, "I have a certain amount of predictive power," Fineberg said. "I can tell you that if an earthquake happens today, at this point, it will progress until this point."

Someday, Fineberg suggests, seismologists may be able to use this information to trigger small earthquakes that prevent large ones.

"That's science fiction right now, very far in the future," he said. "But if we have the essence now in our hands, then maybe we can play with it."

Images: 1) Science/AAAS/Stefano Zapperi 2) The damage after the August 1999 earthquake in Izmit, Turkey. / US Geological Survey.

If you've ever had one (or 10) too many drinks at a bar, you're probably familiar with this scenario: a drunk guy stumbles past you, spills a beer all over you, and you get angry. You're convinced he did it on purpose, and you start fuming. According to a new study in Personality and Social Psychology Bulletin, you've probably fallen victim to one of the many side effects of booze: assuming that others' actions are intentional.

The 92 male participants in the study were led to believe that they were participating in a taste test. After fasting for 3 hours, each subject was given a cold juice drink. For half of the subjects, the drink was pure juice, but the other half were treated to a drink containing more than a shot of pure alcohol.

Within each group, half the participants were told that the drink contained alcohol, and half were not. To complete the illusion, the rims of the glasses of those participants expecting a boozy drink were sprayed with alcohol just before serving.

Once they'd finished the drink and spent some time on unrelated tasks while the alcohol was being absorbed, the subjects were given a series of 50 action statements. Some actions could be interpreted as either deliberate or accidental ("He deleted the email"), some could only be deliberate ("She looked for her keys), and some could only be accidental ("She tripped on the jump rope"). For each statement, the participants had to choose whether the action was done intentionally or unintentionally.

Nearly all the participants, no matter what condition, judged all the unambiguous statements correctly. However, when the actions were ambiguous and could have been performed either intentionally or unintentionally, the "drunk" participants were much more likely to perceive the actions as deliberate than the sober participants were. The clever design of this experiment allowed the researchers to separate the actual physical effects of alcohol from its expectancy effects. What the subjects believed they had consumed didn't affect their responses—only whether they had actually consumed booze or not.

Alcohol makes you much more likely to believe that the guy that knocked into you in the bar is out to get you, instead of recognizing that he probably didn't even see you in his drunken stupor. This biased way of thinking, or "intentionality bias," is a major factor in the link between alcohol and aggression. So, next time you get pissed off at someone after a few drinks, think twice before hitting the guy: he's probably even drunker than you are.